The finale combat against the Nazgul, even if just viewed as a tiebreaker, is a bit disappointing mostly because the only goal for Sauron is stalling long enough. Defeating a hero is so extremely unlikely that the damage caused by the Nazgul is irrelevant to the outcome of this last combat, and thus irrelevant to the outcome of the game.
To improve matters without introducing a slew of new rules, simply go to the Finale rules on p. 34 and add a sentence to step 3 (Prepare):
"Each hero then shuffles all cards from his hand, rest pool, and damage pool into his life pool. Following this, he discards 10 cards plus 1 card for each corruption card he has into his rest pool. Each hero then draws a number of cards from the top of his life pool equal to his fortitude."
This gives the hero a total life of 15 + training – corruption. After drawing cards with fortitude and agility, there will be a buffer of roughly 7 cards before damage goes directly to the hand cards – tough, but absolutely not insurmountable if the Nazgul go for the throat instead of trying to stall.